Development of fluorescence indices to minimise the effects of canopy structural parameters

Remote sensing of sun-induced Chlorophyll fluorescence is a research field of growing interest with the potential to provide an improved tool for monitoring plant status and photosynthetic function. the new satellite mission of the European space Agency (the fluorescence eXplorer, fleX) will provide the possibility to estimate canopy fluorescence from space at global level. However, remote sensing techniques allow measurement of the emitted fluorescence flux but do not provide a direct assessment of the fluorescence yield, which is the key variable linked to the physiological status of the plant. in this study, we investigate the impact of canopy structure on chlorophyll fluorescence by analysing the fluorescence emission in a thinning experiment in a corn field. it is shown that fluorescence and apparent fluorescence yield are well related with leaf area index and vegetation fractional cover, but when fluorescence is divided for a spectral vegetation index (considered as a proxy of structural parameters) the correlation is lost. this means that fluorescence indexes should be considered to take into account spatial and temporal variability of biophysical parameters for satellite studies and promising for plant status applications.